Fighting along the Armenian-Azerbaijani “line of contact” around Nagorno-Karabakh reportedly intensified on Saturday, with the warring sides accusing each other of violating the shaky ceasefire there with heavy artillery fire.

Karabakh’s Armenian-backed Defense Army said Azerbaijani forces have fired since Saturday afternoon more than 250 mortar and howitzer shells and rockets at its positions in northeastern Karabakh and frontline sections east of the Armenian-populated territory. It said one of its soldiers was seriously wounded shortly before the “intensive fire” began.

A statement by the army added that Karabakh Armenian troops responded with actions aimed at “restraining the enemy.” It described the skirmishes as further proof that the Azerbaijani side is not fully complying with a Russian-mediated agreement that stopped heavy fighting in the conflict zone on April 5.

The Azerbaijani Defense Ministry claimed, meanwhile, that the Armenian troops shelled Azerbaijani settlements northeast of Karabakh before trying to launch overnight an “offensive” involving tanks. “The enemy was repelled after approaching Azerbaijani positions,” it said, according to Azerbaijani news agencies.

The Karabakh Defense Army was quick to deny the claim as a “propaganda ploy” designed to cover up Azerbaijani truce violations. It insisted that it has not attempted any offensive operations along “the line of contact” after the April 5 ceasefire agreement reached in Moscow.

Russia’s leaders have since repeatedly urged the conflicting parties to bolster the ceasefire regime. Visiting Yerevan on Friday, Foreign Minister Sergey Lavrov said they should agree to specific safeguards against truce violations without “further delay.” Those include, among other things, international investigations of armed incidents on the Armenian-Azerbaijani frontlines.

Armenia and the Karabakh Armenian leadership support the safeguards sought by the Russian, U.S. and French mediators. Azerbaijan has opposed them until now.

“We will do everything to ensure that the ceasefire holds,” Armenia’s Defense Minister Seyran Ohanian said on Sunday. He said that is essential for creating an “atmosphere of trust” between the parties and thereby reviving the Karabakh peace process.

Ohanian made clear at the same time that the Armenian side is prepared to fight back a fresh Azerbaijani offensive.